In the facsimile transmission and recording of weather maps alone there are, internationally, a diversity of signal sources and transmission modes. The density of the line by line scanning at the signal source may be 48 or 96 lines per inch (LPI) corresponding to a standard known as Index of Cooperation (IOC) of 288 and 576, where: ##EQU1## The time rate of line by line scanning may be 60, 90, 120, 180 or 240 sweeps per minute (SPM). Thus the two line densities and five scan rates impose on the recorder the burden of adjusting to ten different combinations of transmission modes. Additional adjustments are desirable to maintain clear contrast between light and dark portions of the recorded data. Also in some cases it is desirable to extract a portion of the transmitted frame of graphic information and effectively enlarge the portion by recording on an area normally occupied by the whole frame, while maintaining the same aspect ratio as in the normal frame, and maintaining or enhancing the contrast of the enlarged portion.
While all the above mentioned adjustments and compensations can be made piecemeal by separate adjustments of the recorder scanning rate (SPM), the line density and contrast (LPI), it is the object of the present invention to make the adjustments largely automatically in response to the incoming signal so that the recorder does not require constant operator attendance.